LIFE-Moms Phoenix is a randomized controlled trial in obese or overweight pregnant women to test the hypothesis that an intensive lifestyle intervention by trained interventionists using structured group or individual approaches, including daily weights at home, diet and physical activity counseling, psychosocial support, and optional tool box strategies will result in gestational weight gain closer to the IOM recommendations than the control group. The primary outcome is gestational weight gain assessed as a continuous variable. Secondary outcomes include maternal glycemic and metabolic status and complications of pregnancy and delivery, and infant birth weight and adiposity, as well as glycemic and metabolic status at 9-12 months